E.A. Pavlatou, G.N. Papatheodorou, A.K. Rizos, G. Fytas
We report spontaneous Brillouin and photon correlation spectroscopic results on the dynamics of the local density fluctuations in the ionic mixed salt xKNO3⋅yCa(NO3)2 with molar ratios 2:1, 3:2, and 1:1. For these mixtures, the density relaxation function g(t) changes from a stretched exponential (β=0.47) near the glass transition temperature Tg, to an exponential (β=1) form at high temperatures, whereas the composition dependence of the relaxation time τ reflects mainly differences between the Tg values. The 3:2 fragile glass (Tg=60°C) is one of the few examples where g(t) is now known from the glass‐like (60–90 °C) to the liquid‐like (T>100 °C) region through the application of various dynamic scattering techniques. The τ(T) and the evolution of the width β of the distribution are discussed in terms of the physical pictures implied by current models of the liquid and glass transition phase.
doi: 10.1063/1.460731